How a wing makes lift

Tilt a wing into the oncoming air and speed it up, and watch the lift arrow grow against the fixed weight arrow. A wing pushes air downwards, and the air pushes the wing up in return.

The wing is nose-left with the air flowing left to right. The upward arrow is lift and the downward one is the aircraft's weight.

Lift: 19.6kN
Lift ÷ weight: 1.00

What this scene shows, in words

The wing is nose-left with the air flowing left to right. The upward arrow is lift and the downward one is the aircraft's weight.

Air over the top — 14 dots travelling along a path, 5 trips per cycle.
Air under the wing — 12 dots travelling along a path, 3.9 trips per cycle.
Wing — a wing section, nose to the left, 110 wide and 13.3 tall, centred at 0, 0, turned -4 degrees.
Lift — an arrow of length 23.9, pointing 90 degrees anticlockwise from the right.
Weight — an arrow of length 24, pointing 270 degrees anticlockwise from the right.

The values above change as the scene plays and as you move the controls; they are read out again whenever it is paused.

Visual chosen by AI, drawn by our tested code

Assumptions and limits

Assumption: Thin-airfoil lift: 0.11 per degree of angle of attack, with zero lift at minus two degrees for this cambered section.
Assumption: A 16 square metre wing carrying a 2,000 kg aircraft through sea-level air at 1.225 kg per cubic metre.
Limit: Real wings stall past about fifteen degrees and lose their lift; this model does not show that, so the slider stops at twelve.
Limit: The air streams are drawn along fixed paths. Tilting the wing does not bend them, although it would in real air.

Tilt is the first lever

A wing meeting the air at an angle turns that air downwards as it passes. Pushing air down is a force on the air, and the air pushes back on the wing with an equal force upwards: that is lift. The steeper the tilt, the more air is turned and the harder the push, which is why the lift arrow lengthens as you raise the nose. This section is cambered, curved more on top than underneath, so it turns a little air even when it is level and only stops making lift at minus two degrees.

Speed counts twice

Air arriving twice as fast brings twice as much of itself past the wing each second, and each parcel is turned twice as hard. Lift therefore grows with the square of the airspeed: double the speed and the arrow quadruples. That is the whole reason a runway is long. A plane sitting still makes no lift at all, and it has to reach the speed where lift finally equals weight before the wheels can leave the ground.

Set Airspeed to 30 m/s and note the lift arrow falls well short of the weight arrow; now drag Angle of attack up until Lift ÷ weight returns to 1.00.

Check your understanding

A plane is flying level, so lift exactly equals weight. The pilot speeds up without changing the wing's tilt. What happens?

Pick one to check yourself.